EP0318362A1 - Process for the preparation of rare earth borides - Google Patents

Process for the preparation of rare earth borides Download PDF

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Publication number
EP0318362A1
EP0318362A1 EP88402895A EP88402895A EP0318362A1 EP 0318362 A1 EP0318362 A1 EP 0318362A1 EP 88402895 A EP88402895 A EP 88402895A EP 88402895 A EP88402895 A EP 88402895A EP 0318362 A1 EP0318362 A1 EP 0318362A1
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Prior art keywords
rare earth
reaction
chloride
boride
boron
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German (de)
French (fr)
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EP0318362B1 (en
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Alain Iltis
Patrick Maestro
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Rhodia Chimie SAS
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Rhone Poulenc Chimie SA
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B35/00—Boron; Compounds thereof
    • C01B35/02—Boron; Borides
    • C01B35/04—Metal borides

Definitions

  • the present invention relates to a process for the preparation of rare earth borides.
  • rare earths used in accordance with the invention includes the rare earth elements called lanthanides having atomic numbers from 57 to 71 inclusive and the yttrium with atomic number equal to 39.
  • Rare earth borides are products known to have interesting electrical properties.
  • lanthanum hexaboride has excellent thermionic emission properties and is used as an emissive cathode in high energy devices.
  • the applicant proposes a process for the preparation of a rare earth boride, the characteristic of which is to directly obtain an earth boride rare, by heating a rare earth chloride and elemental boron.
  • the preparation of the rare earth boride is carried out according to reaction (1): TrCl3 + (n + 1) B ⁇ TRB n + BCl3 (1)
  • n represents the number of boron atoms per atom of rare earth and is, generally, equal to 4 or 6.
  • the process of the invention allows direct access to the rare earth boride sought after since the only secondary product formed is boron chloride which is volatile, under the reaction conditions.
  • Another advantage of the process of the invention is that it can be implemented in a conventional apparatus, namely an oven with refractory bricks of alumina or alumino-silicates because the reaction temperature is relatively low: it can be chosen lower at 1500 ° C and preferably around 1200 ° C.
  • a chloride of a rare earth whether it is in anhydrous or hydrated form or of a mixture of at least two chlorides of rare earths.
  • the chloride used is of high purity, in particular free of oxygenated impurities such as a residual oxide.
  • a rare earth chloride optionally hydrated, having a purity greater than 95% is used.
  • the drying time can vary between 2 and 24 hours.
  • boron elementary boron can be used, in amorphous or crystallized form.
  • Use is preferably made of a boron free of oxygenated impurities.
  • metallic impurities they are less of a nuisance and it is possible to use a boron having a purity of 85% and more.
  • the quantities of rare earth chloride and boron used are such that the molar ratio between boron and rare earth chloride is preferably at most equal to the reaction stoichiometric quantity and, even more preferably, in slight defect, which can reach from 10 to 20% of the reaction stoichiometric quantity.
  • the first step of the process of the invention consists in carrying out the intimate mixing of the rare earth chloride and of the boron, by dry or wet method.
  • the mixture of powders obtained is then subjected to a heat treatment.
  • the reaction is carried out at a temperature between 1200 ° C and 1500 ° C.
  • a temperature between 1250 ° C and 1300 ° C is chosen.
  • the reaction is carried out at atmospheric pressure, but under an atmosphere of reducing gases and / or inert gases. This is how you can use hydrogen or argon, alone or in a mixture.
  • the duration of the reaction depends on the capacity of the apparatus and its ability to rapidly rise in temperature. Generally, once the desired temperature is reached, it is maintained for a variable period of 1 to 4 hours and, preferably between 1 hour and 2 hours.
  • a rare earth boride and gas evolution which can be boron chloride possibly accompanied by boron oxychloride which can be trapped for example, by bubbling in water.
  • reaction mass is then cooled to ambient temperature (15 to 25 ° C). It is carried out under a reducing and / or inert atmosphere as long as the reaction temperature is not less than 600 ° C.
  • the product is suspended in water, then its separation is carried out according to conventional solid / liquid separation techniques, in particular filtration, decantation, spinning.
  • a rare earth boride is obtained. It is most often a rare earth hexaboride or a rare earth tetraboride depending on the stoichiometric quantities used.
  • the rare earth hexaboride has a cubic elementary cell of the CsCl type. As for the rare earth tetraboride, it crystallizes in the quadratic system.
  • the method of the invention can be implemented in conventional equipment.
  • the mixing of rare earth chloride and boron can be done in a powder mixer of known type: free-fall mixers of the drum type, vertical or horizontal mixers with helical screw, horizontal mixers Lödige type, etc ...
  • the mixture obtained is placed in a nacelle or crucible which may be made of alumina, zirconia, glassy carbon or, preferably, graphite, then the assembly is introduced into a chamber, tunnel, muffle or rotary kiln having a coating classic refractory (alumina or alumino-silicates).
  • This oven is equipped with a device for regulating the temperature during the heat treatment. It must be watertight and allow the circulation of gases (hydrogen, inert). There should be a device for recovering gas emissions, for example, a washing tower.
  • 27.35 g of the said product are mixed with 6.48 g of crystallized boron sold by the company PROLABO, having a purity of 98% and having a particle size varying from 25 to 63 ⁇ m.
  • This mixture is then introduced into a graphite crucible which is placed in a tubular furnace with an alumina refractory coating in which an argon sweep containing 10% by volume of hydrogen is established.
  • the temperature is raised to 1300 ° C and maintained for two hours.
  • reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.
  • the product obtained is washed by suspension in water in order to remove all traces of chloride.
  • the product obtained is cerium hexaboride having an X-ray diffraction diagram in accordance with file ASTM 11670.
  • a powder is obtained having an average particle diameter of 8 ⁇ m and 4 ⁇ m after disintegration of the agglomerates with ultrasound for two minutes.
  • the lanthanum chloride obtained is dried for 24 hours at a temperature of 100 ° C. and under reduced pressure of 1000 Pa.
  • This mixture is then introduced into a graphite crucible which is placed in the tube furnace in which a sweep of argon and hydrogen is established.
  • the temperature is raised to 1250 ° C and maintained for two hours.
  • reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.
  • the product obtained is washed with water.
  • the product obtained which is blue in color, is lanthanum hexaboride having an RX diffraction diagram in accordance with file ASTM 34427.
  • Dehydrated praseodymium chloride is prepared according to the procedure of Example 1.
  • This mixture is then introduced into a graphite crucible which is placed in the tube furnace in which a sweep of argon and hydrogen is established.
  • the temperature is raised to 1250 ° C and maintained for two hours.
  • reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.
  • the product obtained is washed with water.
  • the product obtained which is blue in color, is praseodymium hexaboride having an X-ray diffraction diagram in accordance with file ASTM 251455.
  • cerium chloride CeCl3, 7H2O (purity 99.5%) is dried for 24 hours, at a temperature of 100 ° C. and under reduced pressure of 1000 Pa.
  • This mixture is then introduced into an alumina nacelle which is placed in a tubular oven in which a sweep of argon and hydrogen is established.
  • the temperature is raised to 1250 ° C and maintained for two hours.
  • reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.
  • the product obtained is cerium hexaboride having an X-ray diffraction diagram in accordance with file ASTM 11670.
  • a powder is obtained having particles of 40 ⁇ m and 30 ⁇ m after treatment of two minutes with ultrasound.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
  • Ceramic Products (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
  • Saccharide Compounds (AREA)
  • Hard Magnetic Materials (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

The main feature of the process consists in heating a rare earth chloride and elementary boron.

Description

La présente invention a trait à un procédé de préparation de borures de terres rares.The present invention relates to a process for the preparation of rare earth borides.

L'expression "terres rares" utilisée conformément à l'invention comprend les éléments de terres rares appelés lanthanides ayant des numéros atomiques de 57 à 71 inclus et l'yttrium de numéro atomique égal à 39.The expression "rare earths" used in accordance with the invention includes the rare earth elements called lanthanides having atomic numbers from 57 to 71 inclusive and the yttrium with atomic number equal to 39.

Les borures de terres rares sont des produits connus comme ayant des propriétés électriques intéressantes. En particulier, l'hexa­borure de lanthane possède d'excellentes propriétés d'émission thermoionique et est utilisé comme cathode émissive dans les disposi­tifs de haute énergie.Rare earth borides are products known to have interesting electrical properties. In particular, lanthanum hexaboride has excellent thermionic emission properties and is used as an emissive cathode in high energy devices.

Actuellement, le développement industriel des borures de terres rares est limité en raison de la difficulté d'obtention d'un produit présentant une pureté satisfaisante selon un procédé extrapolable à l'échelle industrielle.Currently, the industrial development of rare earth borides is limited due to the difficulty of obtaining a product having a satisfactory purity according to a process which can be extrapolated to an industrial scale.

Il est connu de préparer le borure de lanthane par réduction du sesquioxyde de lanthane à l'aide du carbure de bore ou de bore élémentaire, sous pression réduite [cf. G. A. Meerson et al - Izv. Akad. Nauk. SSSR Neorg. Mater 3 n° 5 p. 802-806 (1967)]. Toutefois, les réactions étant conduites à des températures supérieures à 1500°C, ceci impose non seulement de faire appel à un creuset en graphite, mais de disposer d'un four ayant un revêtement en graphite.It is known to prepare lanthanum boride by reduction of lanthanum sesquioxide using boron carbide or elemental boron, under reduced pressure [cf. GA Meerson et al - Izv. Akad. Nauk. SSSR Neorg. Mater 3 n ° 5 p. 802-806 (1967)]. However, the reactions being carried out at temperatures above 1500 ° C, this requires not only to use a graphite crucible, but to have an oven having a graphite coating.

On a également proposé selon US-A 3 902 973 de préparer les borures de terres rares, par électrolyse d'une source de terre rare, en milieu sel fondu contenant une cryolite et un borate de métal alcalin. Un tel procédé de préparation est relativement complexe en raison d'une température d'électrolyse comprise entre 950°C et 1050°C et il se pose le problème classique de la récupération du borure de terre rare à la cathode qui, par ailleurs, présente une pollution due à la cryolithe.It has also been proposed according to US-A 3,902,973 to prepare the rare earth borides, by electrolysis of a rare earth source, in a molten salt medium containing a cryolite and an alkali metal borate. Such a preparation process is relatively complex due to an electrolysis temperature between 950 ° C and 1050 ° C and there is the classic problem of recovering rare earth boride at the cathode which, moreover, has pollution due to cryolite.

On rencontre dans le procédé décrit dans US-A 4 260 525, le même problème de séparation du borure de terre rare obtenu : ledit procédé consiste à mélanger le composé carbonate, nitrate ou oxyde de terre rare, avec du bore, en présence d'aluminium pour dissoudre le bore à une température comprise entre 1200°C et 1600°C; à chauffer le milieu réactionnel dans cette gamme de température, à le refroidir, puis à séparer le borure de terre rare, de l'oxyde d'aluminium formé.In the process described in US Pat. No. 4,260,525, the same problem of separating the rare earth boride obtained is encountered: said process consists in mixing the carbonate, nitrate or rare earth oxide compound with boron in the presence of aluminum to dissolve boron to a temperature between 1200 ° C and 1600 ° C; heating the reaction medium in this temperature range, cooling it, then separating the rare earth boride from the aluminum oxide formed.

Pour pallier les inconvénients de séparation et de purification des produits obtenus selon les procédés décrits dans l'état de la technique, la demanderesse propose un procédé de préparation d'un borure de terre rare dont la caractéristique est d'obtenir direc­tement un borure de terre rare, en chauffant un chlorure de terre rare et du bore élémentaire.To overcome the drawbacks of separation and purification of the products obtained according to the processes described in the state of the art, the applicant proposes a process for the preparation of a rare earth boride, the characteristic of which is to directly obtain an earth boride rare, by heating a rare earth chloride and elemental boron.

Conformément à l'invention, on effectue la préparation du borure de terre rare suivant la réaction (1) :
TrCl₃ + (n + 1)B → TRBn + BCl₃ (1)In accordance with the invention, the preparation of the rare earth boride is carried out according to reaction (1):
TrCl₃ + (n + 1) B → TRB n + BCl₃ (1)

Dans ladite réaction, n représente le nombre d'atomes de bore par atome de terre rare et est, généralement, égal à 4 ou 6.In said reaction, n represents the number of boron atoms per atom of rare earth and is, generally, equal to 4 or 6.

Le procédé de l'invention permet d'accéder d'une manière direc­te, au borure de terre rare recherché car le seul produit secondaire formé est le chlorure de bore qui est volatil, dans les conditions de la réaction.The process of the invention allows direct access to the rare earth boride sought after since the only secondary product formed is boron chloride which is volatile, under the reaction conditions.

Un autre avantage du procédé de l'invention est qu'il peut être mis en oeuvre dans un appareillage classique, à savoir un four avec des briques réfractaires en alumine ou alumino-silicates car la température réactionnelle est relativement basse : elle peut être choisi inférieure à 1500°C et, de préférence, aux environs de 1200°C.Another advantage of the process of the invention is that it can be implemented in a conventional apparatus, namely an oven with refractory bricks of alumina or alumino-silicates because the reaction temperature is relatively low: it can be chosen lower at 1500 ° C and preferably around 1200 ° C.

Conformément au procédé de l'invention, on fait appel à un chlorure d'une terre rare qu'il soit sous forme anhydre ou hydratée ou à un mélange d'au moins deux chlorures de terres rares.In accordance with the process of the invention, use is made of a chloride of a rare earth whether it is in anhydrous or hydrated form or of a mixture of at least two chlorides of rare earths.

Il est souhaitable que le chlorure mis en oeuvre soit d'une grande pureté en particulier exempt d'impuretés oxygénées telles qu'un oxyde résiduaire.It is desirable that the chloride used is of high purity, in particular free of oxygenated impurities such as a residual oxide.

On met en oeuvre, de préférence, un chlorure de terre rare éventuellement hydraté ayant une pureté supérieure à 95 %.Preferably, a rare earth chloride, optionally hydrated, having a purity greater than 95% is used.

Toutefois, la présence d'oxychlorure et d'eau n'est pas gênante et l'on peut tolérer une quantité totale pouvant atteindre 20 % en poids.However, the presence of oxychloride and water is not a problem and a total amount of up to 20% by weight can be tolerated.

D'une manière préférentielle, on soumet le chlorure de terre rare à une opération de séchage qui peut être effectuée à une tempé­rature comprise entre 20 et 200 °C, de préférence aux environs de 100°C. Le séchage peut être réalisé à l'air ou, de préférence, sous pression réduite comprise par exemple entre 1 mm de mercure (= 133,322 Pa) et 100 mm de mercure (13 322,2 Pa).Preferably, the rare earth chloride is subjected to a drying operation which can be carried out at a temperature of between 20 and 200 ° C., preferably around 100 ° C. Drying can be carried out in air or, preferably, under reduced pressure of, for example, between 1 mm of mercury (= 133,322 Pa) and 100 mm of mercury (13,322.2 Pa).

La durée de séchage peut varier entre 2 et 24 heures.The drying time can vary between 2 and 24 hours.

En ce qui concerne le bore, on peut avoir recours au bore élémentaire, sous forme amorphe ou cristallisé.As regards boron, elementary boron can be used, in amorphous or crystallized form.

On fait appel, de préférence, à un bore exempt d'impuretés oxygénées. Pour ce qui est des impuretés métalliques, elles sont moins gênantes et l'on peut mettre en oeuvre un bore ayant une pureté de 85 % et plus.Use is preferably made of a boron free of oxygenated impurities. As regards metallic impurities, they are less of a nuisance and it is possible to use a boron having a purity of 85% and more.

Les quantités de chlorure de terre rare et de bore engagées sont telles que le rapport molaire entre le bore et le chlorure de terre rare est, de préférence, au plus égal à la quantité stoéchiométrique réactionnelle et, encore plus préférentiellement, en léger défaut, pouvant atteindre de 10 à 20 % de la quantité stoechiométrique réactionnelle.The quantities of rare earth chloride and boron used are such that the molar ratio between boron and rare earth chloride is preferably at most equal to the reaction stoichiometric quantity and, even more preferably, in slight defect, which can reach from 10 to 20% of the reaction stoichiometric quantity.

La première étape du procédé de l'invention consiste à effectuer le mélange intime du chlorure de terre rare et du bore, par voie sèche ou par voie humide.The first step of the process of the invention consists in carrying out the intimate mixing of the rare earth chloride and of the boron, by dry or wet method.

On soumet ensuite le mélange de poudres obtenu à un traitement thermique. La réaction est effectuée à une température comprise entre 1200°C et 1500°C. D'une manière préférentielle, on choisit une température comprise entre 1250°C et 1300°C.The mixture of powders obtained is then subjected to a heat treatment. The reaction is carried out at a temperature between 1200 ° C and 1500 ° C. Preferably, a temperature between 1250 ° C and 1300 ° C is chosen.

On effectue la réaction à la pression atmosphérique, mais sous atmosphère de gaz réducteurs et/ou de gaz inertes. C'est ainsi que l'on peut faire appel à l'hydrogène ou à l'argon, seuls ou en mé­lange.The reaction is carried out at atmospheric pressure, but under an atmosphere of reducing gases and / or inert gases. This is how you can use hydrogen or argon, alone or in a mixture.

On maintient l'atmosphère des gaz précités, tout au cours de la réaction.The atmosphere of the above gases is maintained throughout the reaction.

La durée de la réaction est fonction de la capacité de l'appa­reillage et de son aptitude à monter rapidement en température. Généralement, une fois la température souhaitée atteinte, on la maintient pendant une durée variable de 1 à 4 heures et, de préfé­rence comprise entre 1 heure et 2 heures.The duration of the reaction depends on the capacity of the apparatus and its ability to rapidly rise in temperature. Generally, once the desired temperature is reached, it is maintained for a variable period of 1 to 4 hours and, preferably between 1 hour and 2 hours.

Au cours de la réaction, il y a formation d'un borure de terre rare et dégagement gazeux qui peut être le chlorure de bore éventuel­lement accompagné d'oxychlorure de bore qui peuvent être piégés par exemple, par barbotage dans l'eau.During the reaction, there is formation of a rare earth boride and gas evolution which can be boron chloride possibly accompanied by boron oxychloride which can be trapped for example, by bubbling in water.

On procède ensuite au refroidissement de la masse réactionnelle jusqu'à température ambiante (15 à 25°C). Il est réalisé sous atmos­phère réductrice et/ou inerte tant que la température réactionnelle n'est pas inférieure à 600°C.The reaction mass is then cooled to ambient temperature (15 to 25 ° C). It is carried out under a reducing and / or inert atmosphere as long as the reaction temperature is not less than 600 ° C.

On récupère directement un borure de terre rare.We recover a rare earth boride directly.

Il peut être souhaitable d'effectuer un ou plusieurs lavages à l'eau, de préférence de un à trois, des chlorures qui peuvent être présents, à titre d'impuretés. A cet effet, on met le produit en suspension dans l'eau, puis l'on effectue sa séparation selon les techniques classiques de séparation solide/liquide, en particulier filtration, décantation, essorage.It may be desirable to carry out one or more washes with water, preferably one to three, of the chlorides which may be present, as impurities. For this purpose, the product is suspended in water, then its separation is carried out according to conventional solid / liquid separation techniques, in particular filtration, decantation, spinning.

Conformément au procédé de l'invention, on obtient un borure de terre rare. Il s'agit le plus souvent d'un hexaborure de terre rare ou d'un tétraborure de terre rare selon les quantités stoechiomé­triques mises en oeuvre. L'hexaborure de terre rare a une maille élémentaire cubique du type CsCl. Quant au tétraborure de terre rare, il cristallise dans le système quadratique.In accordance with the process of the invention, a rare earth boride is obtained. It is most often a rare earth hexaboride or a rare earth tetraboride depending on the stoichiometric quantities used. The rare earth hexaboride has a cubic elementary cell of the CsCl type. As for the rare earth tetraboride, it crystallizes in the quadratic system.

Le procédé de l'invention peut être mis en oeuvre dans un appareillage classique.The method of the invention can be implemented in conventional equipment.

Le mélange du chlorure de terre rare et du bore peut être fait dans un mélangeur à poudres de type connu : mélangeurs à chute libre du type tambour, mélangeurs verticaux ou horizontaux à vis hélicoï­dale, mélangeurs horizontaux type Lödige, etc...The mixing of rare earth chloride and boron can be done in a powder mixer of known type: free-fall mixers of the drum type, vertical or horizontal mixers with helical screw, horizontal mixers Lödige type, etc ...

Le mélange obtenu est placé dans une nacelle ou un creuset qui peut être en alumine, zircone, carbone vitreux ou, de préférence, en graphite, puis l'ensemble est introduit dans un four à chambre, tunnel, à moufles ou rotatif présentant un revêtement réfractaire classique (alumine ou alumino-silicates). Ce four est équipé d'un dispositif permettant de réguler la température au cours du traite­ment thermique. Il doit être étanche et permettre la circulation des gaz (hydrogène, inertes). Il y a lieu de prévoir un dispositif destiné à la récupération des dégagements gazeux, par exemple, une tour de lavage.The mixture obtained is placed in a nacelle or crucible which may be made of alumina, zirconia, glassy carbon or, preferably, graphite, then the assembly is introduced into a chamber, tunnel, muffle or rotary kiln having a coating classic refractory (alumina or alumino-silicates). This oven is equipped with a device for regulating the temperature during the heat treatment. It must be watertight and allow the circulation of gases (hydrogen, inert). There should be a device for recovering gas emissions, for example, a washing tower.

On donne, ci-après, des exemples de réalisation de l'invention présentés à titre illustratif, sans aucun caractère limitatif.Examples of embodiments of the invention are given below, given by way of illustration, without any limiting nature.

Exemple 1Example 1 Préparation d'hexaborure de cériumPreparation of cerium hexaborure

On commence par sécher le chlorure de cérium CeCl₃,7H₂O (pure­té 99,5 %) pendant 24 heures, à une température de 100°C et sous pression réduite de 1000 Pa.We begin by drying the cerium chloride CeCl₃, 7H₂O (purity 99.5%) for 24 hours, at a temperature of 100 ° C and under reduced pressure of 1000 Pa.

On fait le mélange de 27,35 g dudit produit avec 6,48 g de bore cristallisé commercialisé par la Société PROLABO, ayant une pureté de 98 % et présentant une taille de particules variant de 25 à 63 µm.27.35 g of the said product are mixed with 6.48 g of crystallized boron sold by the company PROLABO, having a purity of 98% and having a particle size varying from 25 to 63 μm.

On introduit ensuite ce mélange dans un creuset en graphite que l'on place dans un four tubulaire à revêtement réfractaire en alumine dans lequel on établit un balayage d'argon contenant 10 % en volume d'hydrogène.This mixture is then introduced into a graphite crucible which is placed in a tubular furnace with an alumina refractory coating in which an argon sweep containing 10% by volume of hydrogen is established.

On monte la température jusqu'à 1300°C et on la maintient pendant deux heures.The temperature is raised to 1300 ° C and maintained for two hours.

On laisse ensuite refroidir la masse réactionnelle à l'inertie du four, le balayage gazeux étant maintenu jusqu'à ce que la tempéra­ture devienne inférieure à 600°C.The reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.

On obtient 19,00 g d'un produit bleu-violet.19.00 g of a blue-violet product are obtained.

On effectue un lavage du produit obtenu par mise en suspension dans l'eau afin d'eliminer toute trace de chlorure.The product obtained is washed by suspension in water in order to remove all traces of chloride.

Le produit obtenu est l'hexaborure de cérium ayant un diagramme de diffraction RX conforme à la fiche ASTM 11670.The product obtained is cerium hexaboride having an X-ray diffraction diagram in accordance with file ASTM 11670.

On obtient une poudre ayant un diamètre moyen de particules de 8 µm et de 4 µm après délitage des agglomérats aux ultra-sons pendant deux minutes.A powder is obtained having an average particle diameter of 8 μm and 4 μm after disintegration of the agglomerates with ultrasound for two minutes.

Example 2Example 2 Préparation d'hexaborure de lanthanePreparation of lanthanum hexaborure

On part d'un chlorure de lanthane préparé à partir d'oxyde de lanthane à 99,9 % et d'acide chlorhydrique.We start with a lanthanum chloride prepared from lanthanum oxide at 99.9% and hydrochloric acid.

On sèche le chlorure de lanthane obtenu, pendant 24 heures, à une température de 100°C et sous pression réduite de 1000 Pa.The lanthanum chloride obtained is dried for 24 hours at a temperature of 100 ° C. and under reduced pressure of 1000 Pa.

On fait le mélange de 15 g dudit produit avec 4,62 g de bore cristallisé.15 g of said product are mixed with 4.62 g of crystallized boron.

On introduit ensuite ce mélange dans un creuset en graphite que l'on place dans le four tubulaire dans lequel on établit un balayage d'argon et d'hydrogène.This mixture is then introduced into a graphite crucible which is placed in the tube furnace in which a sweep of argon and hydrogen is established.

On monte la température jusqu'à 1250°C et on la maintient pendant deux heures.The temperature is raised to 1250 ° C and maintained for two hours.

On laisse ensuite refroidir la masse réactionnelle à l'inertie du four, le balayage gazeux étant maintenu jusqu'à ce que la tempé­rature devienne inférieure à 600°C.The reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.

On effectue un lavage à l'eau du produit obtenu.The product obtained is washed with water.

Le produit obtenu, qui est de couleur bleue, est l'hexaborure de lanthane ayant un diagramme de diffraction RX conforme à la fiche ASTM 34427.The product obtained, which is blue in color, is lanthanum hexaboride having an RX diffraction diagram in accordance with file ASTM 34427.

Exemple 3Example 3 Préparation d'hexaborure de praséodymePreparation of praseodymium hexaboride

On prépare du chlorure de praséodyme déshydraté selon le mode opératoire de l'exemple 1.Dehydrated praseodymium chloride is prepared according to the procedure of Example 1.

On fait le mélange de 11 g dudit produit avec 3,059 g de bore cristallisé.11 g of said product are mixed with 3.059 g of crystallized boron.

On introduit ensuite ce mélange dans un creuset en graphite que l'on place dans le four tubulaire dans lequel on établit un balayage d'argon et d'hydrogène.This mixture is then introduced into a graphite crucible which is placed in the tube furnace in which a sweep of argon and hydrogen is established.

On monte la température jusqu'à 1250°C et on la maintient pendant deux heures.The temperature is raised to 1250 ° C and maintained for two hours.

On laisse ensuite refroidir la masse réactionnelle à l'inertie du four, le balayage gazeux étant maintenu jusqu'à ce que la tempé­rature devienne inférieure à 600°C.The reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.

On effectue un lavage à l'eau du produit obtenu.The product obtained is washed with water.

Le produit obtenu, qui est de couleur bleue, est l'hexaborure de praséodyme ayant un diagramme de diffraction RX conforme à la fiche ASTM 251455.The product obtained, which is blue in color, is praseodymium hexaboride having an X-ray diffraction diagram in accordance with file ASTM 251455.

Exemple 4Example 4 Préparation d'hexaborure de cériumPreparation of cerium hexaborure

On sèche le chlorure de cérium CeCl₃,7H₂O (pureté 99,5 %) pendant 24 heures, à une température de 100°C et sous pression réduite de 1000 Pa.The cerium chloride CeCl₃, 7H₂O (purity 99.5%) is dried for 24 hours, at a temperature of 100 ° C. and under reduced pressure of 1000 Pa.

On fait le mélange de 8 g dudit produit avec 2,6039 g de bore technique amorphe contenant 85 % de bore et 12 % de magnésium et présentant une taille de particules de 1,2 µm.8 g of said product are mixed with 2.6039 g of amorphous technical boron containing 85% boron and 12% magnesium and having a particle size of 1.2 μm.

On introduit ensuite ce mélange dans une nacelle en alumine que l'on place dans un four tubulaire dans lequel on établit un balayage d'argon et d'hydrogène.This mixture is then introduced into an alumina nacelle which is placed in a tubular oven in which a sweep of argon and hydrogen is established.

On monte la température jusqu'à 1250°C et on la maintient pendant deux heures.The temperature is raised to 1250 ° C and maintained for two hours.

On laisse ensuite refroidir la masse réactionnelle à l'inertie du four, le balayage gazeux étant maintenu jusqu'à ce que la tempé­rature devienne inférieure à 600°C.The reaction mass is then allowed to cool to the inertia of the oven, the gas sweep being maintained until the temperature drops below 600 ° C.

On effectue trois lavages successifs du produit obtenu, par mise en suspension dans l'eau afin d'éliminer toute trace de chlorure.Three successive washes of the product obtained are carried out, by suspension in water in order to remove all traces of chloride.

Le produit obtenu est l'hexaborure de cérium ayant un diagramme de diffraction RX conforme à la fiche ASTM 11670.The product obtained is cerium hexaboride having an X-ray diffraction diagram in accordance with file ASTM 11670.

Il ne présente aucune impureté cristalline imputable à la présence de magnésium, dans le bore technique.It has no crystalline impurities due to the presence of magnesium in technical boron.

On obtient une poudre ayant des particules de 40 µm et de 30 µm après traitement de deux minutes aux ultra-sons.A powder is obtained having particles of 40 μm and 30 μm after treatment of two minutes with ultrasound.

Claims (16)

1. Procédé de préparation d'un borure d'une terre rare caracté­risé par le fait qu'il consiste à chauffer un chlorure de terre rare et du bore élémentaire.1. A method for preparing a rare earth boride characterized in that it consists in heating a rare earth chloride and elemental boron. 2. Procédé selon la revendication 1 caractérisé par le fait que le borure de terre rare est un hexaborure de terre rare.2. Method according to claim 1 characterized in that the rare earth boride is a rare earth hexaboride. 3. Procédé selon l'une des revendications 1 et 2, caractérisé par le fait que le borure de terre rare est un borure de lanthanides ou d'yttrium.3. Method according to one of claims 1 and 2, characterized in that the rare earth boride is a lanthanide or yttrium boride. 4. Procédé selon l'une des revendications 1 à 3 caractérisé par le fait que le borure de terre rare est l'hexaborure de cérium, de lanthane ou de praséodyme.4. Method according to one of claims 1 to 3 characterized in that the rare earth boride is the hexaboride of cerium, lanthanum or praseodymium. 5. Procédé selon l'une des revendications 1 à 4 caractérisé par le fait que l'on met en oeuvre un chlorure ou un mélange de chlorures de terres rares.5. Method according to one of claims 1 to 4 characterized in that one uses a chloride or a mixture of rare earth chlorides. 6. Procédé selon l'une des revendications 1 à 5 caractérisé par le fait que le chlorure de terre rare est soumis à un séchage entre 20°C et 200 °C à l'air ou sous pression réduite.6. Method according to one of claims 1 to 5 characterized in that the rare earth chloride is subjected to drying between 20 ° C and 200 ° C in air or under reduced pressure. 7. Procédé selon l'une des revendications 1 à 6 caractérisé par le fait que le rapport molaire entre le bore et le chlorure de terre rare est au plus égal à la quantité stoechiométrique.7. Method according to one of claims 1 to 6 characterized in that the molar ratio between boron and rare earth chloride is at most equal to the stoichiometric amount. 8. Procédé selon la revendication 7 caractérisé par le fait que ledit rapport est en léger défaut pouvant atteindre de 10 à 20 % de la quantité stoechiométrique réactionnelle.8. Method according to claim 7 characterized in that said ratio is slightly defective up to 10 to 20% of the reaction stoichiometric amount. 9. Procédé selon l'une des revendications 1 à 8 caractérisé par le fait que la réaction est effectuée entre 1200°C et 1500°C.9. Method according to one of claims 1 to 8 characterized in that the reaction is carried out between 1200 ° C and 1500 ° C. 10. Procédé selon la revendication 9 caractérisé par le fait que ladite température est comprise entre 1250°C et 1300°C.10. The method of claim 9 characterized in that said temperature is between 1250 ° C and 1300 ° C. 11. Procédé selon l'une des revendications 1 à 10 caractérisé par le fait que l'on conduit la réaction sous atmosphère d'hydrogène et/ou de gaz inertes.11. Method according to one of claims 1 to 10 characterized in that the reaction is carried out under an atmosphere of hydrogen and / or inert gases. 12. Procédé selon la revendication 1 caractérisé par le fait que l'on conduit la réaction sous atmosphère d'hydrogène et/ou d'argon.12. Method according to claim 1 characterized in that the reaction is carried out under an atmosphere of hydrogen and / or argon. 13. Procédé selon l'une des revendicatons 1 à 12 caractérisé par le fait que la durée de la réaction varie de 1 à 4 heures.13. Method according to one of claims 1 to 12 characterized in that the duration of the reaction varies from 1 to 4 hours. 14. Procédé selon la revendication 13 caractérisé par le fait que ladite durée est comprise entre 1 et 2 heures.14. The method of claim 13 characterized in that said duration is between 1 and 2 hours. 15. Procédé selon l'une des revendications 1 à 14 caractérisé par le fait que l'on récupère le borure de terre rare, après refroidis­sement jusqu'à température ambiante.15. Method according to one of claims 1 to 14 characterized in that the rare earth boride is recovered, after cooling to room temperature. 16. Procédé selon l'une des revendications 1 à 15 caractérisé par le fait que l'on soumet le produit obtenu à un ou plusieurs lavages à l'eau.16. Method according to one of claims 1 to 15 characterized in that the product obtained is subjected to one or more washes with water.
EP88402895A 1987-11-26 1988-11-18 Process for the preparation of rare earth borides Expired - Lifetime EP0318362B1 (en)

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AT88402895T ATE80594T1 (en) 1987-11-26 1988-11-18 PROCESS FOR THE PRODUCTION OF RARE EARTH BORIDENS.

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FR8716396 1987-11-26
FR8716396A FR2623790B1 (en) 1987-11-26 1987-11-26 PROCESS FOR THE PREPARATION OF RARE EARTH BORURES

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Publication number Priority date Publication date Assignee Title
DE68902769T2 (en) * 1988-04-22 1993-02-25 Rhone Poulenc Chimie METHOD FOR PRODUCING RARE EARTH BORIDES.
FR2803281B1 (en) * 1999-12-29 2002-03-29 Rhodia Terres Rares PROCESS FOR THE PREPARATION OF RARE EARTH BORATES AND THE USE OF BORATES OBTAINED IN LUMINESCENCE
EP1517858A1 (en) * 2002-03-28 2005-03-30 Council Of Scientific And Industrial Research Process for the production of zirconium boride powder
US6967011B1 (en) * 2002-12-02 2005-11-22 The United States Of America As Represented By The United States Department Of Energy Method for synthesizing extremely high-temperature melting materials
CN100427399C (en) * 2006-04-27 2008-10-22 上海交通大学 Method for preparing neodymium hexaboride
RU2448044C2 (en) * 2009-08-03 2012-04-20 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Кабардино-Балкарский государственный университет им. Х.М. Бербекова" Method of producing nanodispersed yttrium hexaboride powder
JP2011063486A (en) * 2009-09-18 2011-03-31 Sumitomo Osaka Cement Co Ltd Method for producing high-purity metal boride particle, and high-purity metal boride particle obtained by the method
JP5910242B2 (en) * 2011-03-29 2016-04-27 住友大阪セメント株式会社 Method for producing lanthanum hexaboride fine particles, lanthanum hexaboride fine particles, lanthanum hexaboride sintered body, lanthanum hexaboride film, and organic semiconductor device
CN102225771B (en) * 2011-04-29 2013-04-10 东北大学 Method for preparing LaB6 nano-powder through mechanical alloying process
RU2477340C2 (en) * 2011-05-13 2013-03-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Кабардино-Балкарский государственный университет им. Х.М. Бербекова" Electrolytic method for obtaining ultradisperse powder of lanthanum hexaboride
EP3835452B1 (en) * 2019-12-09 2024-01-31 The Swatch Group Research and Development Ltd Method for manufacturing a decorative surface
CN113666382A (en) * 2021-09-11 2021-11-19 江西善纳新材料科技有限公司 Preparation method of nano rare earth hexaboride

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE157615C (en) *
NL6804216A (en) * 1968-03-26 1969-09-30

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3258316A (en) * 1963-07-29 1966-06-28 M S A Res Corp Preparation of metal borides
FR2004753A1 (en) * 1968-03-26 1969-11-28 Reactor Ct Nederlan
US3979500A (en) * 1973-05-02 1976-09-07 Ppg Industries, Inc. Preparation of finely-divided refractory powders of groups III-V metal borides, carbides, nitrides, silicides and sulfides
US3902973A (en) * 1973-10-04 1975-09-02 Us Interior Electrolytic preparation of lanthanide and actinide hexaborides using a molten, cryolite-base electrolyte
US4260525A (en) * 1978-11-27 1981-04-07 Rca Corporation Single-crystal hexaborides and method of preparation
DE68902769T2 (en) * 1988-04-22 1993-02-25 Rhone Poulenc Chimie METHOD FOR PRODUCING RARE EARTH BORIDES.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE157615C (en) *
NL6804216A (en) * 1968-03-26 1969-09-30

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Progress in Boron Chemistry", édité par H. STEINBERG et al., vol. 2, no. 3, 1970, page 193, MacMillan Co., New York, US *
CHEMICAL ABSTRACTS, vol. 93, no. 22, décembre 1980, page 141, résumé no. 206964w, Columbus, Ohio, US; A.I. KARASEV et al.: "Study of conditions for the production of technical-grade samarium, europium, and gadolinium hexaborides under pilot-plant conditions", & TUGOPLAVKIE SOEDIN. REDKOZEM. MET., [MATER. VSES. SEMIN.], 3rd 1977 (Pub. 1979), 32-4 *

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FR2623790A1 (en) 1989-06-02
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EP0318362B1 (en) 1992-09-16
ATE80594T1 (en) 1992-10-15
US5176890A (en) 1993-01-05
JPH0581526B2 (en) 1993-11-15
DE3874689T2 (en) 1993-03-04
FR2623790B1 (en) 1990-11-30
KR890008026A (en) 1989-07-08
ES2035347T3 (en) 1993-04-16
AU2593888A (en) 1989-06-01
JPH01230423A (en) 1989-09-13
DE3874689D1 (en) 1992-10-22
BR8806171A (en) 1989-08-15

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